science
posted by bittubeniwal .
What is the acceleration of a tennis ball if initially it comes toward the player's racquet at 20 m/s, and it leaves in the opposite direction at 24 m/s? A highspeed camera indicates the time of impact of 4.0 ms.

Find the overall average speed of swimmer number one during the race.
Find the overall average speed of the second swimmer from the time he starts swimming until he ends his race.
What is the instantaneous speed of the second swimmer at time t = 25 s during the race?
What is the average acceleration of the second swimmer during the time interval starting at ti = 25 s and ending at tf = 50 s?
What is the average acceleration of the second swimmer during the time interval starting at ti = 25 s and ending at tf = 35 s?
What is the average acceleration of the first swimmer during the time interval starting at ti = 10 s and ending at tf = 30 s?
A car brakes from 60 mi/h to a full stop in 4 seconds. Find the acceleration of the car during this time interval in m/s2.
What distance did the car in problem 15 travel in the time since first applying the brakes?
A cheetah resting in the savanna sees her prey and accelerates from rest to 70 mi/h in 6.2 seconds. Assuming she moves with a constant acceleration, find this acceleration and the distance she ran when she first reaches 30 mi/h.
After what distance did the cheetah reach 70 mi/h?
Find the fall time for an object dropped from an altitude of 25,000 meters, neglecting air drag (i.e., the time it takes the bullet in the previous ยท example to return to the starting point, from the time it reached its maximum height).
Suppose the bullet is still effective in piercing sheet metal at a speed of 100 m/s. What is the maximum altitude at which you could still use this bullet to fight an aerial attack?
To find the depth of a well, you drop a small pebble and time its fall until you hear the splash of the pebble on the water surface below. What is the depth of the well if the time you got is 3.25 seconds? Consider that sound propagates almost instantaneously from the surface of the water to your ear.
What is the depth of the well if we take into account the finite sound speed in air of 334 m/s?
A mouse is dropped from an eagle's claws starting at an altitude of 150 meters. What distance does it fall in the first second after it is dropped?
What distance does the mouse in problem 23 travel in the third second of its free fall?
At what speed does the mouse in problem 23 hit the ground? 
I don't know